Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
12-21-2010, 03:47 PM   #1
New Member




Join Date: Dec 2010
Location: Colorado
Posts: 11
Aperture not working

Greetings,

I have acquired an 100mm f/4 Macro Takumar (SMC) that appears to have an issue with its aperture. It has an M42 mount with aperture lugs for metering without stopping down on my Spotmatic SPF. I cannot get it to stop down either manually or while on the camera when taking an exposure. Are there any tips on how to diagnose and fix this problem?

Thanks,

Tony

12-21-2010, 03:59 PM   #2
Veteran Member




Join Date: Feb 2009
Location: Alameda, CA
Posts: 3,206
There is a tiny pin on the lens mount. While depressing this pin (you may need something like the tip of a ballpoint pen), turn the A/M ring on the lens to M.
12-21-2010, 07:04 PM   #3
New Member




Join Date: Dec 2010
Location: Colorado
Posts: 11
Original Poster
I tried depressing both pins but neither seems to engage the aperture. Moreover, my 50mm f/2 SMC Takumar works fine on the camera, but the 100mm macro does not, even though they have the same mount.

Thanks
12-22-2010, 11:57 AM   #4
Site Supporter
Site Supporter
Just1MoreDave's Avatar

Join Date: Feb 2007
Location: Aurora, CO
Photos: Gallery | Albums
Posts: 6,335
I'm not sure about the Spotmatic F, so for simplicity, I'll skip it. With the lens off the camera, screw a rear cap on. That should press the tiny pin in. BTW, the tiny pin is a few degrees CCW of the square block on the mount, half-hidden here, not the larger chrome pin at the top:



Now slide the AUTO/MAN. switch so it says MAN. Set the aperture ring to f16 or so and the aperture blades should close. They should move whenever you change the aperture ring setting.

If you can't set the switch to MAN., it's that damned tiny pin. If you can get the switch to MAN. and still the blades don't move, the lens has to be disassembled for repair. The problem might be the blades or the aperture mechanism, both involving a lot of disassembly.

12-23-2010, 01:32 PM   #5
New Member




Join Date: Dec 2010
Location: Colorado
Posts: 11
Original Poster
Thanks for the info. Depressing the small pin and setting to manual does not resolve the problem, so it looks like a disassembly will be required.
12-23-2010, 08:14 PM - 1 Like   #6
Site Supporter
Site Supporter
Just1MoreDave's Avatar

Join Date: Feb 2007
Location: Aurora, CO
Photos: Gallery | Albums
Posts: 6,335
The blades might have oil on them (not typical for Takumars to get so oily they don't move) or a spot of rust sticking them together (seen this twice). Or the mechanism might be jammed, maybe it was dropped. The typical Takumar construction looks like my photo above, with no screws in the mount. There might be tiny screws in the DOF scale but they don't do anything except loosen the scale. So you have to start at the other end. I haven't seen this particular lens but it usually goes like this: unscrew the trim ring that says SMC Takumar 100/4 etc. It unscrews via the filter threads. Then you'll see 3 screws that hold on the filter thread barrel, take those off and the barrel comes off. Three more screws hold the focus ring on, remove those and the focus ring. Then those DOF scale screws finally become useful; remove them and the scale. Now slide off the aperture ring, being careful not to lose the bearing trapped between the ring and lens body, right where the orange diamond is. The aperture ring hides 3 screws that can be removed, and then you can take off the lens mount. To get to the aperture blades, you may have to remove front and rear lens groups. At that point construction varies but the screws aren't hidden any more so you can probably puzzle it out.
12-24-2010, 05:48 PM   #7
New Member




Join Date: Dec 2010
Location: Colorado
Posts: 11
Original Poster
Thanks Dave, for that information. I've come up with another bit of info about the lens. When it is set to manual, the larger pin only slowly raises back out if depressed. However, when in auto the pin pops right back after being depressed. Does this have any diagnostic value?

Thanks,

Tony

Reply

Bookmarks
  • Submit Thread to Facebook Facebook
  • Submit Thread to Twitter Twitter
  • Submit Thread to Digg Digg
Tags - Make this thread easier to find by adding keywords to it!
aperture, k-mount, pentax lens, slr lens
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
I'm having a funny problem with aperture. It's not working as it shold be learnphotography Pentax DSLR Discussion 20 04-04-2010 11:32 PM
Vivitar 85-205mm 2.8/f aperture not working Minoltaguy Pentax SLR Lens Discussion 0 03-29-2010 09:33 PM
K200d and weird non working aperture. zelovoc Pentax DSLR Discussion 3 12-13-2009 02:38 AM
SEARS 80-200mm aperture not working michalko99 Pentax SLR Lens Discussion 1 08-24-2009 09:44 AM



All times are GMT -7. The time now is 04:34 AM. | See also: NikonForums.com, CanonForums.com part of our network of photo forums!
  • Red (Default)
  • Green
  • Gray
  • Dark
  • Dark Yellow
  • Dark Blue
  • Old Red
  • Old Green
  • Old Gray
  • Dial-Up Style
Hello! It's great to see you back on the forum! Have you considered joining the community?
register
Creating a FREE ACCOUNT takes under a minute, removes ads, and lets you post! [Dismiss]
Top